Fine grain silver halide emulsions containing novel dye combinations

ABSTRACT

FINE GRAIN PHOTOGRAPHIC SILVER HALIDE EMULSIONS ARE SPECTRALLY SENSITIZED WITH THE COMBINATION OF (1) A CARBOCYANINE DYE HAVING A MAXIMUM SENSITIVITY PEAK AT A WAVELENGTH SHORTER THAN 6563 A., AND (2) A CARBOCYANINE DYE HAVING A MAXINUM SENSITIVITY PEAK AT A WAVELNGTH LONGER THAN 6563 A.; EACH OF THE DYES COMPRISING HETEROCYCLIC NUCLEI SELECTED FROM A 3-SULFOALKYLBENZOTHIAZOLE NUCLEUS, A 3-SULFOALKYLBENZOELENAZOLE NUCLEUS AND A 1SULFOALKYLNAPHTHO(1,2-D) THIAZOLE NUCLEUS, THE TWO HETEROCYCLIC NUCLEI OF EACH OF SAID DYES BEING JOINED BY A TRIMETHINE CHAIN WHICH CONTAINS AN ALKYL GROUP ON THE MESO CARBON ATOM THEREOF.

"United States Patent 3,573,920 FINE GRAIN SILVER HALIDE EMULSIONS CON-TAINING NOVEL DYE COMBINATIONS Gary L. Hiller, Rochester, N.Y., assignorto Eastman Kodak Company, Rochester, N.Y.

No Drawing. Continuation-impart of abandoned application Ser. No.686,831, Nov. 30, 1967. This application Sept. 5, 1968, Ser. No. 757,789

Int. Cl. G03c 1/22, 1/28 US. Cl. 96-104 41 Claims ABSTRACT OF THEDISCLOSURE Fine grain photographic silver halide emulsions arespectrally sensitized with the combination of (1) a carbocyanine dyehaving a maximum sensitivity peak at a wavelength shorter than 6563 A.,and (2) a carbocyanine dye having a maximum sensitivity peak at awavelength longer than 6563 A.; each of the dyes comprising heterocyclicnuclei selected from a 3-sulfoalkylbenzothiazole nucleus, a3-sulfoalkylbenzoselenazole nucleus and a 1-sulfoalkylnaphtho[1,2-d]thiazole nucleus, the two heterocyclic nuclei ofeach of said dyes being joined by a trimethine chain which contains analkyl group on the meso carbon atom thereof.

This application is a continuation-in-part of my copending US.application Ser. No. 686,831, filed Nov. 30, 1967 now abandoned.

This invention relates to novel combinations of cyanine dyes forextending the sensitivity of photographic silver halide emulsions tocertain wavelength radiations in the red region of the spectrum, andmore particularly to novel silver halide emulsions containing thesenovel dye combinations, and to photographic elements prepared therewith.

It is Well known in the art of making photographic silver halideemulsions that certain cyanine dyes in combination extend thesensitivity of photographic silver halide emulsions in greater degreethan do the individual dyes in such emulsions. This effect has oftenbeen referred to in the prior art as a kind of supersensitization. Suchproposed combinations in conventional emulsions having an average silverhalide grain size greater than about 0.5 micron have been found usefulin a number of photo graphic applications. However, none have provedentirely satisfactory for use in recording certain narrow bands in thered region of the spectrum. For example, in the field of recording solaror astronomical observations, none of the proposed combinations haveshown the required sensitivity and desired freedom from graininess ofimage for satisfactory recording of the H-u line which lies at 6563 A.This is also true in the field of information recording, where it isdesirable to obtain maximum speed at this line with a minimum ofgraininess in the image. There is evident need, therefore, for new andimproved photographic materials having good speed and maximumsensitivity in a relatively narrow band centered at about 6563 A.

It is, accordingly, an object of this invention to provide novel cyaninedye combinations for extending the sensitivity of photographic silverhalide emulsions to the red region of the spectrum with maximumsensitivity occurring at about 65 63 A. Another object of this inventionis to provide novel silver halide emulsions capable of accuraterecording of fine detail at about 6563 A. Another object of thisinvention is to provide photographic elements comprising a supportmaterial having at least one layer thereon containing a novel emulsionof the invention. Other objects will be apparent from this disclosureand the appended claims.

I have now made the surprising discovery that highly advantageous dyecombinations comprising (1) certain carbocyanine dyes having a maximumsensitivity peak at a Wavelength shorter than 6563 A. and preferablyfrom about 6350 A. to 6550 A. (i.e., 635 to 655 nm.) and (2) certainclosely related carbocyanine dyes having a maximum sensitivity peak at awavelength longer than 6563 A. and preferably from about 6600 A. to 6850A. (i.e., 660 to 685 nm.) are particularly useful for extending thespectral sensitivity range of fine grain photographic silver halideemulsions. These emulsions are useful for recording a variety ofwavelength exposures. They are especially useful for recording finedetail of astronomical observations through narrow band exposures whichmay have a band width of /2 transmission (i.e., as measured at the 50transmission point) of 0.5 A. to 3.0 A. These dye combinations, I havefurther discovered, have the added advantage that they increase theinherent blue speed of fine grain emulsions, and reduce granularity by afactor of 4 or 5 times over that of larger, coarser grained emulsionsheretofore employed in this recording field. The increased inherent bluespeed obtained with the dye combination is particularly unexpectedbecause the dyes, When used individually or even in combinations have asubstantial desensitizing effect on the inherent blue speed ofconventional emulsions, i.e., emulsions having an average silver halidegrain size greater than about 0.5 micron. Furthermore, the novel dyecombinations of the invention give homogeneous and smooth flowing finegrain emulsions having excellent keeping stability, and cause little, ifany, fogging in fresh or incubated emulsions. Accordingly, thisinvention provides photographic materials well suited for recording theradiations in the above specified region of 6563 A. in fine detail.

From the foregoing description, it will be apparent that the principaladvantages of this invention, as compared with prior art proposals, maybe summarized as follows:

(1) Increased inherent blue speed of fine grain emulslons;

2) Increased speed at 65 63 A. for recording fine detail; and

(3) Improvement in granularity over other products that use the H-a lineexposure.

As used herein and in the appended claims, the term fine grain refers tosilver halide emulsions wherein the silver halide grains have an averagegrain size of less than about 0.5 micron, and preferably about from 0.04to 0.40 micron.

The novel dye combinations of the invention comprise (1) a carbocyaninedye having maximum sensitivity peak at a wavelength shorter than 6563A., and preferably from about 635 to 655 nm., and (2) a carbocyanine dyehaving maximum sensitivity peak at a wavelength longer than 6563 A., andpreferably from about 660 to 685 nm., said dyes 1) and (2) in eachinstance comprising first and second heterocyclic nuclei selected fromthe group consisting of a 3-sulfoalkylbenzothiazole nucleus, a 3-sulfoalkylbenzoselenazole nucleus, and al-sulfoalkylnaphtho[1,2-d]thiazole nucleus, the two heterocyclic nucleiof each dye being joined together by a trimethine linkage having analkyl group substituted at the mesocarbon atom thereof.

The proportions of the dyes employed in the dye combinations of theinvention can vary over practically any limits and still give goodresults; however, the most efiicacious combinations are those containingthe respective dyes in the proportions of about from 10 to 90% by weightof dye (1) and conversely about from 90 to 10% by weight of dye (2). Thetotal amount of these dyes is advantageously about from 0.10 to 1.0 gramper mole of silver.

The preferred carbocyanine dye compounds (1) of the invention havemaximum sensitivity at a wavelength of about 635 to 655 nm., and includethose dyes represented by the following formula:

wherein R represents an alkyl group (preferably a lower alkyl containingfrom 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl,butyl, etc.; R and R each represents a sulfoalkyl group, e.g.,B-sulfoethyl, 'y-sulfopropyl, 'y-sulfobutyl, w-sulfobutyl, etc.; and Zand Z each represents the non-metallic atoms necessary to complete abenzothiazole nucleus, e.g., benzothiazole, 5-chlorobenzothiazole,S-bromobenzothiazole, S-methoxyhenzothiazole, 5 butoxybenzothiazole, 5methylbenzothiazole, 5butylbenzothiazole, and the like nuclei.

The preferred carbocyanine dye compounds (2) of the invention havemaximum sensitivity at a wavelength of from about 660 to 685 nm., andinclude those dyes represented by the following formula:

wherein R R and R each represents a value given for R, R and Rrespectively; and, Z and Z each represents the non-metallic atomsnecessary to complete a heterocyclic nucleus selected from (a) whereineach of Z and Z is a benzoselenazole nucleus, e.g., benzoselenazole,S-methoxybenzoselenazole, S-methylbenzoselenazole, etc., (b) whereineach of Z and Z is a naphtho- [1,2-d] thiazole nucleus, and (c) whereinZ is a naphtho- [1,2-d] thiazole nucleus and Z is a benzothiazolenucleus.

It will be understood that certain mono salts of the dyes defined byFormulas I and II above are included in these definitions, since suchsalts improve the solubility of the dyes without materially altering thesensitivity maximum peaks thereof. For example, useful mono salts of thedyes are alkali metals such as the monosodium, the monopotassium etc.salts, the mono salts of the dyes with trialkylamines such as themonotriethylamine, etc. salts, and the like.

The following dyes designated Dye 0-1 and Dye C-II are representative ofthe prior art (outside this invention) and are included herein only forcomparison purposes.

C-II 3,3,9-triethy1'5,5-diehloro-thiacarbocyanine bromide.

D ye

III Anhydro-5,5-dichlin'o-9-ethyl-3,3-di(4-sulfobutyl) thiacarbocyaninehydrox e.

1 0 Compound 1 CH2) 4 S 0 H cyanine hydroxide.

30 V Anhydr0-9-ethyl-5,5-dimethyl-3,3-di(3-sulfopropyl) thiacarbocyaninehydroxide, triethylamine salt.

Included among the carbocyanine dyes defined by Formula II above are thefollowing typical dye compounds.

Dye No. Compound VI Anhydro-Q-ethyl-fi-methoxy-3,3-di(3-sulfopropyl)selenacarbocyanine hydroxide, sodium salt VIIIAnhydro-9-ethyl-3,3-di(3-su1fopropyl)-4,5-benzothiacarbocyaninehydroxide, sodium salt The above Dyes III to VII and related dyes have,in general, been previously described in the prior art and are prepared,for example, by the general methods set forth in R. H. Sprague US. Pat.No. 2,503,776, issued Apr. 11, 1950; and A. E. Rosenoff U.S. Pat. No.3,177,- 210, issued Apr. 6, 1965.

PREPARATION OF DYE VIII A mixture of 2.7 g. (1 mol.)anhydro-2-methyl-3-(3- sulfopropyl)benzothiazolium hydroxide and 4.1 g.(1 mol.) of anhydro-Z-(Z-ethoxy 1butenyl)-1-(3-sulfopropyl)naphtho[1,2-d]thiazolium hydroxide in 25 ml.of cresol is refluxed for 2 minutes. The mixture is chilled, stirredwith an excess of ether, the ether decanted from the sticky residue,more ether added with stirring, and the ether again decanted. Theresidue is treated with 5.1 g. of sodium iodide in 300 ml. of acetone,with stirring. The dye precipitates as the monosodium salt and iscollected on a filter funnel, washed with acetone and dried. The yieldof dye is 4.3 g. (66%), MP. 244245 C.

The above intermediate anhydro-2-(2-ethoXy-l-butenyl) 1 (3sulfopropyl)naphtho[1,2-d]thiazolium hydroxide is prepared by refluxingfor a period of 5 minutes a mixture of 64.2 g. (1 mol.) of anhydro-2-methyl-1(3-sulfopropyl)naphthol[1,2 d]thiazolium hydroxide and 70.4 g.(1 mol. +100% excess) of triethyl orthopropionate in 70 ml. of distilledcresol. On cooling the mixture the product crystallizes from solution.The light green solid is then collected, washed with acetone and dried.The crude yield of this compound 2o 23 4 2) is 64 g. (79%).

According to the invention, one or more of the carbocyanine dyesrepresented by Formula I above are incorporated with one or more of thecarbocyanine dyes rep resented by Formula II above. The invention isparticularly directed to fine grain gelatino-silver-halidedeveloping-out emulsions, including fine cubic grain silver halideemulsions. However, the dye combinations can also be employed in silverhalide emulsions in which the carrier or vehicle is a hydrophiliccolloid other than gelatin, such as for example, albumin, agar-agar, gumarabic, alginic acid, etc., or a hydrophilic resin such as polyvinylalcohol, polyvinyl pyrrolidone, a cellulose ether, a partiallyhydrolyzed cellulose acetate, acrylamide polymers, etc., which has nodeleterious effect upon the light-sensitive silver halide. The dyes ofFormula I and Formula II can be employed in the combinations of theinvention in various concentrations depending upon the particularemulsion, concentration of the silver halide, particular resultsdesired, etc. The optimum concentration of an individual sensitizing dyecan be determined in a manner Well known to those skilled in the art bymeasuring the sensitivity of a series of test portions of the sameemulsion, each portion containing a different concentration of thesensitizing dye. As previously mentioned, the preferred combinationsrange about from to 90% to the carbocyanine dye of Formula I andconversely about from 90 to 10% of the carbocyanine dye of Formula II.The optimum concentration of the dye combinations can, of course, bereadily determined in the same manner, by measuring the sensitivity of aseries of test portions of the same emulsion, each portion containingdifferent concentrations of the individual dyes in the combination. Indetermining the optimum concentration for the subject dye combinations,it is advantageous to employ, at first concentrations of the individualdyes less than their optimum concentrations. The concentrations of theindividual dyes can be increased until the optimum concentration of thedye combination is determined.

The methods of incorporating sensitizing dyes in silver halide emulsionsare well known to those skilled in the art and these known techniquesare employed in dispersing the dyes of the invention in the emulsions.These dyes can be directly dispersed in the emulsions, or they can firstbe dissolved in some convenient solvent, such as pyridine, methylalcohol, acetone, etc. (or mixtures of such solvents), or diluted withwater in some instances, and added to the emulsions in the form of thesesolutions. If desired, the dyes can be separately dissolved in a givensolvent and added separately to the emulsion, or they can be dissolvedin the same or different solvent and these solutions mixed togetherbefore addition is made to the silver halide emulsions. The dyes of theinvention can be dispersed in the finished emulsions and should beuniformly distributed throughout the emulsions before the emulsions arecoated on a suitable support, such as paper, glass, cellulose esterfilm, polyvinyl resin film (e.g., polystyrene film, polyvinyl chloridefilm, etc.), polyester film, etc. The following procedure has been foundquite satisfactory: Stock solutions of the dyes of Formulas I and IIabove are prepared by separately dissolving these dyes in appropriatesolvents as described above. Then, to the flowable silver halideemulsion, the desired amount of stock solution of one of the dyes isslowly added while stirring the emulsion. Stirring is continued untilthe dye is thoroughly incorporated in the emulsion. Then, the desiredamount of stock solution of the other dye is slowly added to theemulsion while stirring. Stirring is continued until the second dye isthoroughly incorporated in the emulsion. The emulsions can then becoated on a suitable support and the coating allowed to dry. In someinstances, it may be desirable to heat the sensitized emulsion for a fewminutes before coating onto the suitable support. The details of suchcoating techniques are well known to those skilled in the art. Theforegoing procedure and proportions are to be regarded only asillustrative. Clearly, the invention is directed to any fine grainsilver halide emulsion containing a combination of the aforesaid dyeswhereby a supersensitizing effect is obtained, e.g., gelatino silverchloride, -chlorobromide, -chloroiodide, chlorobromoiodide, bromoiodide,etc., emulsions.

The fine grain emulsions employed in accordance with this invention canbe prepared in any suitable manner, such as by the process described inthe article entitled Properties of Photographic Emulsion Grains by Kleinand Moisar, The Journal of Photographic Science, vol. 12, 1964, pages242-245; or, by the method described by Illingsworth in French Patent1,497,202 and corresponding U.S. patent application Ser. No. 500,366,filed Oct. 21, 1965, and now abandoned by maintaining, during emulsionprecipitation, a pH of no more than 4.0 and the pAg within the range of8.6 to 9.2. Also useful are the very fine grain silver halide emulsionprepared in the presence of an acid substituted aryl mercaptan, e.g.,thiosalicylic acid, as described by Sutherns in U.S. patent applicationSer. No. 622,034, filed Mar. 10, 1967, and now U.S. Pat. No. 3,519,427.

The invention is further illustrated by the following examples.Comparison Example 1 employs prior art coarse grain silver halide.

Example 1 This example illustrates the desensitizing effect of theindividual dyes defined by Formulas I and II and certain combinationsthereof on conventional type emulsions when incorporated therein. Thedyes are added to a silver bromoiodide emulsion containing 0.77 molepercent iodide of the type described by Trivelli and Smith, Phot.Journal, 79, 330 (1939), and having an aver-age grain size of 0.75micron. The individual dyes and dye combinations, dissolved in suitablesolvents, are added to separate portions of the emulsion at theconcentrations indicated in Table 1 hereinafter. In each case, afterbeing digested at about 50 C. for 10 minutes, the emulsion is coated ata coverage of 432 mg. silver per square foot on a cellulose acetate filmsupport. A sample of each coating is exposed on an Eastman IBSensitometer through Kodak Wratten Filters 35 +38A to determine bluesensitivity and to a wedge spectrograph, processed for three minutes inKodak Developer D-l9 which has the following composition:

G. N-methyl-p-aminophenol sulfate 2.0 Hydroquinone 8.0 Sodium sulfite(desiccated) 90.0 Sodium carbonate (monohydrate) 52.5 Potassium bromide5.0

Water to make 1.0 liter.

and then fixed in a conventional sodium thiosulfate fixing bath, washedand dried. Densitometric measurements are then made of the developedimages of each coating. The relative speed values are calculated basedon an arbitrary relative speed of 100 for the control containing no dye.The results are listed in the following table together with thesensitizing ranges and maximum sensitivities.

sitize conventional silver halide emulsions having an average silverhalide. grain size above 0.5 micron.

Example 2 This example illustrates that the combination of dyes of theinvention defined by Formulas I and II above greatly increase therelative speed of fine grain emulsions, in the desired maximumsensitivity region of 6563 A., as compared with (a) the speed of theindividual dyes in the same fine grain emulsion, and (b) as comparedwith the speed of the prior art combination of Dye C-I and Dye C-II inboth the fine grain and in the large coarse grain emulsion, which latteris arbitrarily set at 100 for comparison purposes. The procedure for theabove testing is as follows.

A fine grain silver bromoiodide gelatin emulsion is prepared inessentially the same manner as described in Example 1 of IllingsworthUS. patent application Ser. No. 500,366 filed Oct. 21, 1965, and issulfur and gold sensitized. The average grain size of the silver halidecrystals in this fine grain emulsion is of the order of about 0.35micron. Also prepared is a coarse grain 0.75 micron emulsion duplicatingthat of above Example 1. The dyes comprising comparison Dyes C-I and 0-Hand Dyes III to VIII of the invention are incorporated individually, andin certain combinations thereof in separate portions of the aboveemulsions, specific concentrations, as indicated in Table 2 hereinafter.A control of the fine grain emulsion containing no dye is also includedin this table. After digestion at C. for 10 minutes, each of the samplesis then coated at a coverage of 450 mg. silver per square foot on acellulose acetate film support. The cured coatings are then exposed andprocessed by the procedure described in above Example 1. Thesensitization ranges and the relative blue speed and the relative speedat 6563 A. are measured. The results are recorded in the following Table2.

TABLE 2 601107 dye, Sensitization Relative speed g. m e range Dye N0.silver (nm.), to Blue At 6,563 A.

0.75,. emulsion c-1 and 0-11...{ 700 106 100 0.85;. emulsion Control 0.00 71 730 58 69 0.20 700 78 o. 30 700 76 73 0.15 750 91 0.15 750 1070.15 800 118 132 0.20 756 112 13s III+VI 8: 750 118 174 III-l-VII 95%?790 91 182 0.125 IV+VI 075 740 92 V+VI 8: 760 123 166 1v+vn 8: 780 118166 V+VIII 8: 750 126 Referring to above Table 1, it will be seen thatthe relative blue speed for each of the dyes and dye combinations listedis substantially less than that shown for the control containing no dye.This result clearly shows that the dyes employed in this inventionactually desen- Referring to above Table 2, it will be noted that thedye combinations of the invention provide fine grain emulsions andphotographic elements therewith that are characterized by markedlyincreased relative speeds ranging from 145 to 182 at the desired 6563 A.line, as

compared to the prior art combination of Dyes C-I and C-II showing inthe 0.75 and the 0.35 1 emulsions relative speeds of only 100 and 60,respectively, for this spectral line.

Example 3 This example illustrates the significant improvement ingranularity of the novel fine grain emulsions of the inventioncontaining the novel dye combinations. RMS granularities (see I. H.Altman The Measurement of RMS Granularity, Applied Optics, vol. 3, No.1, January 1964, pp. 35-38) are run and plotted at a density of 0.6 logE above fog. For this test, the same fine grain emulsion is used for thedye combinations of the invention, while the same 0.75 micron grain sizeemulsion is used for the prior art dye combination (C-I and C-II), asdescribed in above Example 2. Also, the same coating and processingprocedures are carried out in each case, as set forth in Example 2. Theresults are listed in the following Table 3 wherein the higher thenumber shown for granularity, the grainier is the sample tested.

TABLE 3 Dye cnc., g./1 nole silver Dye No.

o-I and CII rv+vn IV+VL Control By reference to above Table 3, it willbe seen that the lowest granularity, i.e., 0.35, is recorded by the finegrain control sample, and that the samples containing the dyecombinations of the invention (IV+VII, and IV+VI) show only a moderateincrease in granularity over the control to 0.6. In contrast thereto,the prior art sample containing the dye combination C-I and C-II shows arelatively large value for granularity of 3.0. These results clearlyindicate that the novel emulsions and elements of the invention are 4 or5 times less grainy as compared to the conventional prior art largegrain emulsion sample containing the dye combination of C-1 and C-II.

Fine grain photographic silver halide emulsions such as those listedabove, containing the dye combinations of the invention can also containsuch addenda as chemical sensitizers, e.g., sulfur sensitizers (e.g.,allyl thiocarbamate, thiourea, allylisothiocyanate, cystine, etc.),various gold compounds (e.g., potassium chloroaurate, auric trichloride, etc. (see Baldsiefen, U.S. Pat. No. 2,540,085, issued Feb. 6,1951; Damschroder, U.S. Pat. No. 2,597,- 856, issued May 27, 1952 andYutzy et a1. U.S. Pat. No. 2,597,915, issued May 27, 1952), variouspalladium compounds such as palladium chloride (Baldsiefen, U.S. Pat.No. 2,540,086, issued Feb. 6, 1951), potassium chloropalladate (Stautferet al., U.S. Pat. No. 2,598,079, issued May 27, 1952), etc., or mixturesof such sensitizers; antifoggants such as ammonium chloroplatinate(Trivelli et al. U.S. Pat. No. 2,566,245, issued Aug. 28, 1951),ammonium chloroplatinite (Trivelli et al., U.S. Pat. No. 2,566,263,issued Aug. 28, 1951), benzotriazole, nitrobenzimidazole, 5nitroimidazole, benzidine, mercaptans, etc. (see Mees-The Theory of thePhotographic Process, MacMillan Pub., 1942, page 460), or mixturesthereof. The fine grain photographic silver halide emulsions containingthe dye combination of the invention can be hardened with any suitablehardener, including aldehyde hardeners such as formaldehyde, andmucochloric acid, aziridine hardeners, hardeners which are derivativesof dioxane, oxypolysaccharides such as oxy starch or oxy plant gums, andthe like. The emulsion layers can also contain additional additives,particularly those known to be beneficial in photographic emulsions,including, for example, lubricating materials, stabilizers, speedincreasing materials, absorbing dyes, plasticizers, and the like. Thesephotographic emulsions can also contain in some cases additionalspectral sensitizing dyes. Furthermore, these emulsions can containcolor forming couplers or can be developed in solutions containingcouplers or other color generating materials. Among the useful colorformers are the monomeric and polymeric color formers, e.g., pyrazolonecolor formers, as well as phenolic, heterocyclic and open chain couplershaving a reactive methylene group. The color forming couplers can beincorporated into the photographic silver halide emulsions using anysuitable technique, e.g., techniques of the type shown in Jelley et al.U.S. Pat. 2,322,027, issued June 15, 1943, Fierke et al. U.S. Pat.2,801,171, issued July 30, 1957, Fisher U.S. Pats. 1,055,155 and1,102,028, issued March 4, 1913 and June 30, 1914, respectively, andWilmanns U.S. Pat. 2,186,849 issued Jan. 9, 1940. They can also bedeveloped using incorporated developers such as polyhydroxybenzenes,aminophenols, 3-pyrazolidones, and the like.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof, it willbe understood that variations and modifications can be efiected withinthe spirit and scope of the invention as described hereinabove, and asdefined in the appended claims.

I claim:

1. A fine grain photographic silver halide emulsion wherein said silverhalide grains have an average grain size within the range of 0.04 toless than 0.5 micron, containing a dye combination comprising (1) 10 toby weight of a carbocyanine dye having a maximum sensitivity peak at awavelength shorter than 6563 A., and (2) 90 to 10% by weight of acarbocyanine dye having a maximum sensitivity peak at a wavelengthlonger than 6563 A., said dyes (1) and (2) each comprising first andsecond heterocyclic nuclei selected from the group consisting of a3-sulfoalkylbenzothiazole nucleus, a 3-sulfoalkylbenzoselenazole nucleusand a l-sulfoalkylnaphtho [1,2-d]thiazole nucleus, said first and secondnuclei of each dye being joined together by a trimethine linkage whichis substituted on the meso carbon thereof by an alkyl group, the totalweight of the dye combination present in the emulsion being an amounteffective to spectrally sensitize said emulsion.

2. A fine grain emulsion in accordance with claim 1 wherein said silverhalide has an average grain size of about from .04 to 034 micron.

3. A fine grain emulsion in accordance with claim 1 containing a colorformer.

4. A fine grain emulsion in accordance with claim 1 wherein the totalweight of said dyes is about from 0.10 to 1.0 gram per mole silver.

5. A fine grain emulsion in accordance with claim 1 wherein saidemulsion is a silver bromoiodide emulsion.

6. A fine grain emulsion in accordance with claim 1 wherein said dye (1)has a maximum sensitivity peak at from about 635 to 655 nm., and saiddye (2) has a maximum sensitivity peak at from about 660 to 685 nm.

7. A fine grain photographic silver halide emulsion wherein said silverhalide grains have an average grain size within the range of from about0.04 to less than 0.5 micron, containing a dye combination of (1) 10 to90% by weight of a carbocyanine dye having a maximum sensitivity peak atfrom about 635 to 655 nm. and represented by the formula:

and (2) 90 to by weight of a carbocyanine dye having a maximumsensitivity peak at from about 660' to 685 nm. and represented by theformula:

wherein R and R each represents an alkyl group containing from 1 to 4carbon atoms; R R R and R each represents a sulfoalkyl group containing1 to 4 carbon atoms; Z and Z each represents the non-metallic atomsnecessary to complete a benzothiazole nucleus; and Z and Z eachrepresents the non-metallic atoms necessary to complete a heterocyclicnucleus selected from the group consisting of: (a) wherein each of Z andZ is a benzoselenazole nucleus; (b) wherein Z and Z each represents anaphtho[l,2-d]thiazole nucleus; and, (c) wherein Z is anaphtho[1,2-d]thiazole nucleus and Z is a benzothiazole nucleus, thetotal weight of dye combination present in the emulsion being an amounteffective to spectrally sensitize said emulsion.

8. A fine grain emulsion in accordance with claim 7 wherein said silverhalide has an average grain size of about from .04 to 0.4 micron.

9. A fine grain emulsion in accordance with claim 7 containing a colorformer.

10. A fine grain emulsion in accordance with claim 7 wherein the totalweight of said dyes is from 0.10 to 1.0 gram per mole of silver.

11. A fine grain emulsion in accordance with claim 7 wherein saidemulsion is a silver bromoiodide emulsion.

12. A fine grain photographic silver halide emulsion wherein said silverhalide grains have an average grain size within the range of 0.04 toless than 0.5 micron, containing a dye combination comprising (1) 10 to90% by weight of the dye anhydro-S,5-dichloro-9-ethyl-3,3-di(4-sulfobutyl)-thiacarbocyanine hydroxide and (2) 90 to 10% by weightof the dye anhydro-9-ethyl-5-methoxy- 3,3 di(3 sulfopropyl)selenacarbocyanine hydroxide, sodium salt, the total weight of dyecombination present in the emulsion being an amount effective tospectrally sensitize said emulsion.

13. A fine grain emulsion in accordance with claim 12 wherein saidsilver halide has an average grain size of about from .04 to 0.4 micron.

14. A fine grain emulsion in accordance with claim 12 wherein saidsilver halide emulsion is a silver bromoiodide emulsion.

15. A fine grain photographic silver halide emulsion wherein said silverhalide grains have an average grain size within the range of 0.04 toless than 0.5 micron, containing a dye combination comprising (1) 10 to90% by weight of the dye anhydro-5,5'-dichloro-9-ethyl-3,3'-di(4-sulfobutyl)-thiacarbocyanine hydroxide and (2) 90 to 10% by weightof the dye anhydro-9-ethyl-3,3'-di(3- sulfopropyl -4,5 ;4',5'-dibenzothiacarbocyanine hydroxide salt, the total weight of dyecombination present in the emulsion being an amount effective tospectrally sensitize said emulsion.

16. A fine grain emulsion in accordance with claim 15 wherein saidsilver halide has an average grain size of about from .04 to 0.4 micron.

17. A fine grain emulsion in accordance with claim 15 wherein saidsilver halide emulsion is a silver bromoiodide emulsion.

18. A fine grain photographic silver halide emulsion wherein said silverhalide grains have an average grain size within the range of 0.04 toless than 0.5 micron, containing a dye combination comprising (1) 10 to90% by weight of the dye anhydro-S,5-dichloro-9-ethyl-3,3-di(3-sulfobutyl)-thiacarbocyanine hydroxide and (2) 90 to 10% by weightof the dye anhydro-9-ethyl-5-metlioxy-3,3-di(3-sulfopropyl)-selenacarbocyanine hydroxide salt, the totalWeight of dye combination present in the emul- 12 sion being an amounteffective to spectrally sensitize said emulsion.

19. A fine grain emulsion in accordance with claim 18 wherein saidsilver halide has an average grain size of about from .04 to 0.4 micron.

20. A fine grain emulsion in accordance with claim 18 wherein saidsilver halide emulsion is a silver bromoiodide emulsion.

21. A fine grain photographic silver halide emulsion wherein said silverhalide grains have an average grain size Within the range of 0.04 toless than 0.5 micron, containing a dye combination comprising (1) 10 toby weight of the dye anhydro-9-ethyl-5,5-dimethyl-3,3-di(3-sulfopropyl)-thiacarbocyanine hydroxide salt and (2) 90 to 10% byweight of the dye anhydro-9-ethyl-5-methoxy-3,3 -di 3-sulfopropyl-selenacarbocyanine hydroxide salt, the total weight of dye combinationpresent in the emulsion being an amount effective to spectrally semitizesaid emulsion.

22. A fine grain emulsion in accordance with claim 21 wherein saidsilver halide has an average grain size of about from .04 to 0.4 micron.

23. A fine grain emulsion in accordance with claim 21 wherein saidsilver halide emulsion is a silver bromoiodide emulsion.

24. A fine grain photographic silver halide emulsion wherein said silverhalide grains have an average grain size within the range of 0.04 toless than 0.5 micron, containing a dye combination comprising (1) 10 to90% by Weight of the dye anhydro-S,5-dichloro-9-ethyl-3,3'-di(3-sulfobutyl)thiacarbocyanine hydroxide and (2) 90 to 10% by weight of thedye anhydro-9-ethyl-3,3'-di(3-sulfopropyl) 4,5;4',5dibenzothiacarbocyanine hydroxide salt, the total weight of dyecombination present in the emulsion being an amount effective tospectrally sensitize said emulsion.

25. A fine grain emulsion in accordance with claim 24 wherein saidsilver halide has an average grain size of about from .04 to 0.4 micron.

26. A fine grain emulsion in accordance with claim 24 wherein saidsilver halide emulsion is a silver bromoiodide emulsion.

27. A fine grain photographic siliver halide emulsion wherein saidsilver halide grains have an average grain size within the range of 0.04to less than 0.5 micron, containing a dye combination comprising (1) 10to 90% by Weight of the dye anhydro-9-ethyl-5,5'-dimethyl-3,3'-di(3-sulfopropyl)-thiacarbocyanine hydroxide salt and (2) 90 to 10% byweight of the dye anhydro-9-ethyl-3,3'-di (3-sulfopropyl)-4,5benzothiacarbocyanine hydroxide salt, the total weight of dyecombination present in the emulsion being an amount effective tospectrally sensitize said emulsion. v

28. A fine grain emulsion in accordance with claim 27 wherein saidsilver halide has an average grain size of about from .04 to 0.4 micron.

29. A fine grain emulsion in accordance with claim 27 wherein saidsilver halide emulsion is a silver bromoiodide emulsion.

30. A photographic element comprising a support coated with at least onelayer of a fine grain photographic silver halide emulsion of claim 1.

31. A photographic element comprising a support coated with at least onelayer of a fine grain photographic silver halide emulsion of claim 7.

32. A photographic element comprising a support coated with at least onelayer of a fine grain silver halide emulsion of claim 12.

33. A photographic element comprising a support coated with at least onelayer of a fine grain photographic silver halide emulsion of claim 15.

34. A photographic element comprising a support coated with at least onelayer of a fine grain photographic silver halide emulsion of claim 18.

35. A photographic element comprising a support coatedwith at least onelayer of a fine grain photographic silver halide emulsion of claim 21.

36. A photographic element comprising a support coated with at least onelayer of a fine grain silver halide emulsion of claim 24.

37. A photographic element comprising a support coated with at least onelayer of a fine grain silver halide emulsion of claim 27.

38. A fine grain photographic silver halide emulsion wherein said silverhalide grains have an average grain size within the range of from about0.04 to less than 0.5 micron, containing a dye combination of (l) 10 to90% by weight of a carbocyanine dye having a maximum sensitivity peak atfrom about 635 to 655 nm. and represented by the formula:

and (2) 90 to 10% by Weight of a carbocyanine dye having a maximumsensitivity peak at from about 660 to 685 nm. and represented by theformula:

/'Z2\ I l l 1 l e R5'NC=CH|C=O=NR9 wherein R and R each represents analkyl group; R R R and R each represents a sulfoalkyl group; Z and Zeach represents the non-metallic atoms necessary to complete abenzothiazole nucleus; and, Z and Z each represents the non-metallicatoms necessary to complete a heterocyclic nucleus selected from thegroup consisting of: (a) wherein each of Z and Z is a benzoselenazolenucleus; (b) wherein Z and Z each represents a naphtho [l,2-d]thiazolenucleus; and, (c) wherein Z is a naphtho[1,2-d]thiazo1e nucleus and Z isa benzothiazole nucleus, the total weight of dye combination present inthe emulsion being an amount effective to spectrally sensitize saidemulsion.

39. A fine grain emulsion in accordance with claim 38 containing a colorformer.

40. A fine grain emulsion in accordance with claim 38 wherein the totalWeight of said dyes is from 0.10 to 1.0 gram per mole.

41. A fine grain emulsion in accordance with claim 38 wherein saidemulsion is a silver bromoiodide emulsion.

References Cited UNITED STATES PATENTS 2,533,426 12/1950 Carroll et a196-l04 NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, AssistantExaminer US. Cl. X.R. 96106

